Although various hierarchical structures have been investigated with respect to the different elements of urban form, the hierarchical spatial order of access from streets to plots and buildings has not been adequately explicated and objectively assessed. In this article, a new method, access structure, is presented to bridge this knowledge gap. Based on Krop’s generic multilevel diagram of urban form, different types of access structure are developed and symbolically represented. They are then quantitatively measured and compared using three metrics and an associated ternary diagram. Subsequently, the new method is tested first in analysing the internal structure of an individual urban block and then in distinguishing urban blocks with different structural characteristics. Eight urban blocks across the city of Nanjing, China, are selected as case examples. The results show that access structure is capable of accurately describing and evaluating complex spatial relationships between streets, plots and buildings. Access structure is potentially a useful method for studying the complex emerging built form of rapidly changing cities, especially in developing countries such as China.

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During urban renewal, multi-story residential blocks face a contradiction of balancing residential capacity improvement and solar constraint. This paper constructed a set of automatic workflows for adding new volumes to existing buildings, and a multi-objective optimization was applied with a Wallacei plug-in in Grasshopper to optimize the solar radiation, solar hours, and block capacity. First, this study established three building addition modes of existing blocks in the horizontal direction, vertical direction, and mixed direction, respectively. Three optimization objectives—maximum floor area ratio, maximum average radiation amount, and minimum solar shade—were defined. Second, the net increase in the floor area ratio of the block was calculated to balance capacity improvement and solar constraint. Third, the advantages of the three addition modes under different orientations were discussed. Among all three modes, the mixed addition mode had the best capacity improvement effect, with a 70% increase in floor area ratio. The vertical addition mode had the least impact on the solar shade of existing buildings. The horizontal addition mode could further improve the floor area ratio in areas where building height was strictly limited. The results can provide insights and inspiring guidelines for the renewal of the existing residential blocks to solve the floor area ratio constraint from solar radiation, as well as achieve urban function reconstruction and vitality regeneration.

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A superblock is a core unit of the built form of an old city in China, in which various morphological elements are organized and related through a hierarchical structure. Existing quantitative studies are generally limited to a single perspective or object and do not support the classification of morphological types through comprehensive analysis methods. In this study, a new cognitive framework, the hierarchy matrix, is presented to bridge this knowledge gap. It consists of four dimensions: configuration of network, geometry of network, configuration of area, and geometry of area. These dimensions are formed by the intersection of the two coordinates of perspective and object. Based on their measurement, the overall characteristics of the superblocks are represented and compared through matrix diagrams. Subsequently, the validity and adaptability of this quantitative approach are verified through an empirical analysis of Nanjing’s old city superblocks. The results reveal the morphological type of superblocks, and their causes are analyzed through the correlation with the urban environmental background. hierarchy matrix is potentially a useful method for studying the complex emerging built form of rapidly changing cities, especially in developing countries, such as China. The hierarchical matrix method is not only an analysis tool but also has the potential to develop an evaluation method to provide scientific support for the practice of urban renewal.

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